When users first hear of iCloud's new per-app security model, one of the first reactions is a fear that their documents are now stuck inside that one app, and can't be shared. This isn't actually an issue however. If you want to move a screenshot from Preview to Photoshop, for example, you can still save the graphic file explicitly to the Desktop or any other location from within Preview. You can also search for the file in the Finder and "Open With" whatever app you'd like.

This is because Apple has given users the implied permission to do anything they want to do with their files. When you move a file out of iCloud, or tell the Finder to open an iCloud-saved document with another app, the system immediately grants you permission to do this on the fly, just as if a user copies a file they want to share from their secure home directory to a file server accessible by other users.

For example, if you Spotlight search for a TextEdit document you've saved to iCloud, the document appears in the Finder and can be opened in another application, such as Pages, even though that app doesn't currently even support iCloud yet. The system handles the duplication and local saving of that file, and Pages can begin working on it just as if iCloud never existed. The original document remains in iCloud, tied to TextEdit. Pages (or any other app) can work on its copy, and save it to the file system just as always. It doesn't get the benefits of iCloud, but it also doesn't suffer from any new artificial limitations imposed by iCloud security.

On the other hand, rogue apps that try to go around the user's back and maliciously access, edit or destroy a user's iCloud documents will simply find those documents are off limits to them. Mountain Lion sandboxes apps from accessing iCloud files belonging to another application unless the user has specifically indicated that they want to provide access. This creates an important new security barrier that significantly hampers the potential for spyware, viruses and other malware to do bad things to your data, all without creating any real new hoops or hassles for users to navigate.

The only way a piece of malware can access iCloud documents is if it can orchestrate a "social attack" that convinces users to manually copy each of their app's iCloud files into a non-secure area, a much more difficult task than simply getting itself installed within the local file system and then wrecking havoc on all the files located there. iCloud's new per-app security is as big of a leap ahead as user permissions were for OS X a decade ago.

Get ready for the future of documents

Greatly increased security isn't the only benefit of iCloud of course; once your app's documents are in the cloud, you can access them from any other Mac and from your mobile iOS devices. You don't have to think about how to move documents around, and don't have to manage different versions (that's done by the system, which can roll back changes thanks to the Versions feature (below), no need for saving separate copies of each of your files, each with different names or stored in different folders).

Apple didn't just think up iCloud and its security model in the last year; it's been in the works for a long time. And during that time, the company has rolled out a series of foundational technologies that enable it to work, from Spotlight indexing (so you can find cloud-based files as quickly as local ones) to AutoSave and Versions (so you don't have to manually manage each incremental change of a document at specific intervals, each being saved as its own file) to Time Machine's graphical backup and restore user interface. And of course, iCloud's unique interface and security characteristics also borrow from iOS.

These all contribute to automating the file system so users don't have to deal with it directly. iOS devices have always had a local file system; it's just not visible and exposed to the user. In the future of OS X, file level operations (and security) will increasingly be handled by the system itself so you don't have to set up and manage complex hierarchies of files that are at risk of being lost when a hard drive mechanism fails or when a specific bit of hardware is lost or compromised by malware.

iCloud doesn't solve every problem. Unlike DropBox, you can't currently share your iCloud files with other users directly, or manage on a folder level what files are being synced where. It isn't a solution for storing huge files such as gigabytes of video, something that other cloud storage solutions do address. It also isn't a way to put files on the web for sharing (as iDisk once did).

Apple may adapt iCloud's feature set to handle new tasks like these in the future, but for now, iCloud offers users a much simpler way to work with their documents, increased security, increased mobility between devices, and lays the foundation for secure cross platform file access, something that will be pioneered by Apple's own iWork apps once Mountain Lion ships.

Get ready for the future of data, too

In addition to greater security and simplicity in handling documents, recall that iCloud also offers app developers a way to securely store bits of data, as Safari, Reminders and Notes already do in Mountain Lion. This is also an important new leap in bridging the divide between different computers tied and between the desktop and mobile devices.

Developers can now offer to store users' data, from a checklist of items like Reminders to a bit of state like the open tabs in Safari, and make them available via iCloud to a mobile app. Developers can already build their own mechanisms for moving data around between Macs, or between their OS X and iOS apps, but iCloud provides a secure, central and simple way to offload this task onto Apple's servers.

And because both iOS and OS X users are now prompted to set up a free iCloud account when they begin using their system, developers can be reasonably assured that the majority of users already have an iCloud account (unlike MobileMe, which was only used by a few million paying users).

The upside to using iCloud for sharing data between systems and between Apple's desktop and mobile platforms is enhanced simplicity for developers, enhanced reliability for users (as each developer isn't tasked with working the bugs out of their own home-rolled data sharing system), and again, vastly increased security from malware intrusions like spyware and viruses. Once iCloud becomes the primary way to store such data and private documents, even successful viruses will find they have nothing of value to snoop and little they can maliciously destroy, even if they can manage to get themselves installed.

The downside to iCloud

What's not to like about iCloud? Apple's integration and security work on iCloud does intrench its position as the most successful mobile device provider. That means users will have a new impediment to trying alternatives, such as a Google branded tablet or a Microsoft branded phone. You can still buy competing devices, but Apple's iCloud will make the alternatives less attractive for the same reason the App Store makes it less attractive to peruse options that can't run iOS apps.

On the desktop, while Apple supplied an iDisk client for Windows users under .Mac and MobileMe, there's not really any way to make iCloud's documents broadly available to Windows users (without defeating its entire security model). That means iOS users who save their mobile documents to iCloud will have to go out of their way to manually email or otherwise export those documents to a Windows PC or tablet.

In addition the the proprietary "Walled Garden" nature of iCloud that ties it to Apple's own desktop and mobile platforms, users also can't shop around for iCloud storage; Apple's servers are the only option. There's no way for Google or Microsoft or Dropbox to set up a server that iCloud users can use instead. That means if you become dependent upon the service, your only option is to pay Apple for extra storage after you exhaust your initial free allocation.

Of course, you can still use cloud storage offerings from vendors such as Google, Microsoft and Dropbox just as you can use other companies' email, calendar and contacts accounts. They just won't work in the same integrated way that iCloud does. And of course, other vendors offer their own proprietary, integrated services and features that aren't available to Apple.

Additionally, while Apple can claim that iCloud is the only significant cloud-based service that hasn't suffered a major security debacle resulting in the loss of user's data (unlike Google, Microsoft, Palm, Nokia, and seemingly everyone else), that's really only the case because Apple changed the name of MobileMe, which launched as an embarrassing fiasco and never managed to pick itself up off the ground. Apple has a lot to prove in the area of being competent in providing reliable, scalable network services.

Under MobileMe, downtime was largely just a brief annoyance (in part because nobody was taking it seriously). With iCloud, Apple has raised the stakes dramatically, because iCloud incorporates a variety of services, including Documents in the Cloud, which are critical to have available at all times. So far, Apple seems to have put sufficient resources into iCloud to shed the perception that it just isn't very good at tasks beyond its core competency of building software platforms and the hardware devices that run them. It still has some ways to go however.

As a whole, iCloud offers a compelling solution to the complexity and security issues of the conventional security system, bridges the gap between desktops and mobiles, and opens up the potential for all kinds of new cloud sharing features in third party apps. And it does so without erecting any artificial anticompetitive barriers to alternative cloud services. For both users and developers, iCloud represents a great leap forward. For Apple's direct competitors, it represents a significant competitive challenge, as long as Apple can prove itself competent at hosting the cloud services it has rapidly billowed out over the last year.

While this all sounds nice, and theoretically might be a nice DB replacement, it just doesn't work right now.

The major file app vendors, Readdle and GoodReader, have both attempted to implement iCloud support on their apps, and both have failed. One has pulled the feature, and the other sent me a support request stating "iCloud as implemented does not seem to work very well."

Omni, one of the best developers for the Mac desktop, has similarly given up on attempting to use iCloud to sync for its apps that are not using its own servers (OmniOutliner for example.)

So -- while this all looks pretty, and may work between Macs with 10.8, it does not appear to be functional yet for mobile devices. Perhaps some necessary bits are not there yet until iOS6.

Here's to hoping this all works out in our favor, but the rollout of this has been weak. Don't expect a Dropbox replacement anytime soon. SJ should have paid for them when he met with them, whatever price they wanted.

iCloud files aren't that sandboxed away. From Finder or Terminal, you can navigate to ~/Library/Mobile Documents to see a list of folders corresponding to iCloud-supported apps. For example, com~apple~TextEdit, where inside you'll find all your TextEdit files. You can even put files there manually and they'll show up in TextEdit's iCloud interface. I've actually made use of this with iFiles as a generic cloud storage option between OSX and iOS.

These remarkable new technologies will basically kill Microsoft and the Windows ecosystem. There's no way they can compete with this deep level integration across all devices only consumers want: Apple devices. Game over Microsoft.

These remarkable new technologies will basically kill Microsoft and the Windows ecosystem. There's no way they can compete with this deep level integration across all devices only consumers want: Apple devices. Game over Microsoft.

Never used SkyDrive ? or Office 365, or the new Office 2013 ?

These are not "remarkable new technologies". They are great technologies, as long as you're not locked in, and it's great they are also available in the apple eco-system

Ok, I have a real problem with the term "Cloud". Back when the Internet was just opening up to businesses and the general public, technical presenters would draw a network diagram on a whiteboard and represent the Internet as this Cloud picture. That's about all Cloud really means. The cloud represented the Internet at large. ie.. don't worry about it, it's out there in the Cloud. Jobs in 1997 wasn't talking cloud he was talking NFS distributed storage. I recently read an article about how a developer setup a cloud to do his work on an iPad. Well in reality he rented a Unix shell account from a provider, remotely connected to that shell using Secure Shell SSH. Utilized GNU Screen (or tmux) to maintain a connection on the remote host even if he lost his actual connection. This meant he could pickup where he left off if his iPad lost it's 3G connection, etc. Add in a Bluetooth keyboard and essentially what you have is a 25+ year old VT100 dumb terminal that happens to have a roaming cellular data connection and WiFi and it fits in your bag and has a 10 hour battery life. Course it's just a Unix shell prompt and the developer did everything in ViM/eMacs/SFTP/SSH. etc.

What "Cloud" is really all about is merely high speed, redundant, distributed, storage, and virtual machines. Take all that virtual technology, let it replicate across data centers, give it huge amounts of super fast storage and 10GbE/Fiber data transfer speeds and suddenly you have a Cloud that can be public or private. The term Cloud is a buzzword catch all for all this new way of thinking about data centers.

So what we have is technology that's been around for decades all coming together to make something new. The advances in CPU's to optimize virtual machines made the largest advance. Now SSD technology is starting to build super fast caches for disk arrays, that will eventually replace physical disks with SSD disks. Virtual machines in many nodes and clusters and software virtual networking inside the virtual environment (no physical Cisco rack equipment, etc. except at the Rack level). Running just about any operating system inside the virtual machines and pushing the hardware to maximum levels so you are not wasting electricity or physical space. (i.e. used to have entire racks running 85% idle waiting for a sudden peak load at say quarter end processing, etc. Now you have Virtual Machines taking up that idle 80% and allowing for a burst of processing only when you need it. i.e. allocate additional CPU's, RAM, and disk I/O when necessary).

iCloud just sync's at the moment, what little storage you are provided is merely short term 30 days or so. Photostream is no different than document storage It just pushes the documents and App data back to all your devices. It won't keep it on the Cloud servers forever or you will certainly need to buy more storage and perhaps that will start happening soon. Don't need to keep your data in the Cloud if it's sync'ing across multiple devices. Your laptop, desktop, iPad, and iPhone would have to be destroyed at the same time to lose everything.